What is the purpose of stretching slack after coupling?

Stretching slack after coupling serves several important purposes related to train operations, particularly in ensuring proper coupler alignment. When train cars are coupled together, there may be some initial slack in the couplers due to variations in the track, the weight of the train, or the design of the couplers themselves. By stretching the slack, the couplers are pulled taut, which helps align them correctly and secures the connection between the cars.

Proper coupler alignment is crucial for safe train operation because misaligned couplers can cause undue stress on the train's components, increase the risk of derailment, and lead to mechanical failures. When slack is stretched, it allows the automatic and manual systems of the train to work efficiently by ensuring that the couplers are engaged properly, which is essential for the effective operation of the braking system and overall train handling. Thus, performing this action is vital for maintaining the integrity and safety of the train setup.